Simian virus 40 (SV40) is a monkey virus that was administered to human populations by contaminated vaccines which were produced in SV40 naturally infected monkey cells.Recent molecular biology and epidemiological studies suggest that SV40 may be contagiously transmitted in humans by horizontal infection, independently from the earlier administration of SV40-contaminated vaccines.SV40 footprints in humans have been found associated at high prevalence with specific tumor types such as brain and bone tumors, mesotheliomas and lymphomas and with kidney diseases, and at lower prevalence in blood samples from healthy donors.Contrasting reports appeared in the literature on the circulation of SV40 in humans by contagious transmission and its association, as a possible etiologic cofactor, with specific human tumors. As a consequence of the conflicting results, a considerable debate has developed in the scientific community. In the present review we consider the main results obtained by different groups investigating SV40 sequences in human tumors and in blood specimens, the putative role of SV40 in the onset/progression of specific human tumors, and comment on the hypotheses arising from these data.

Merkel cell polyomavirus (MCPyV), a DNA tumor virus, has been found to be associated with Merkel cell carcinoma and chronic lymphocytic leukemia. MCPyV sequences have also been detected in various normal tissues in tumor-affected patients. Immunologic studies have detected MCPyV antibodies in as many as 80% of healthy blood donors. This high seroprevalence suggests that MCPyV infection is widespread in humans. In our study, buffy coats, which were examined for MCPyV DNA Tag sequences, showed a prevalence of 22%. Viral DNA load was revealed in blood samples from 10 to 100 molecules/100 000 cells. DNA sequencing confirmed that polymerase chain reaction amplicons belong to the IntroductionMerkel cell polyomavirus (MCPyV) is a small DNA tumor virus. 1 A recent investigation has reported MCPyV sequences in 27.1% of purified malignant cells from human chronic lymphocytic leukemia (CLL) samples. 2 CLL, the most common leukemia in the Western world, results from the expansion of a rare population of mature B-lymphocytes. 3 In a previous study, MCPyV DNA was identified in Merkel cell carcinoma (MCC). 4 This neoplasm is a rare but aggressive skin cancer of neuroendocrine origin. 5 MCC has been detected in immunosuppressed patients who have undergone organ transplantation or are affected by HIV infection, with Tlymphocyte immunosuppression resulting from CLL. 6 MCPyV DNA has been also identified in various tissue samples in patients affected by malignant or nonmalignant tumors. 4,[7][8][9] Moreover, the presence of MCPyV in peripheral blood at low copy number has also been reported. 4,10 Recent immunologic studies have detected MCPyV antibodies in 70% to 80% of adults. 11-13 Because human polyomavirus DNAs have been detected in tonsillar tissues, the high respiratory tract has been proposed as one of the entry portals for these viral agents. 14-16 However, the process by which polyomaviruses, and specifically MCPyV, gain access to and establish persistent infections in distal body compartments has not been well established. 15 Methods Samples and PCR techniquesBuffy coats (n ϭ 60) were obtained from healthy blood donors as recently described. 17 DNA was isolated as previously done, and its quality was confirmed by ␤-globin polymerase chain reaction (PCR). 17 The pUC57MC1 recombinant plasmid, with MCC 350 strain sequences, was used as a positive control in MCPyV PCR amplification experiments. 18 Two different MCPyV Tag regions, nucleotides (nt) 571 to 879 and nt 1709 to 1846, were investigated by single PCR analysis for 35 cycles using the primer sets, LT3F-LT3R and MCPyLT1709.FMCPyLT1864.R, respectively. Amplicons of 308 bp and 138 bp are expected from these sPCR amplifications. 4,18 However, no MCPyV Tag sequences were detected in our samples. Recently, similar data have been reported by other groups. 19,20 To verify whether these negative data were the result of a low viral DNA load in our buffy coats, the same MCPyV sequences were investigated by PCR reamplifications, using 5 L of the first PCR reaction, with the same ...

In this study, we compared the pharmacological and biochemical characteristics of A 2B adenosine receptors in recombinant (hA 2B HEK293 cells) and native cells (neutrophils, lymphocytes) by using a new potent 8-pyrazole xanthine derivative, showing the presence of A 2B mRNA. The rank order of potency of typical adenosine ligands with recombinant hA 2B receptors was consistent with that typically found for interactions with the A 2B subtype and was also similar in peripheral blood cells. 5Ј-N-Ethylcarboxamidoadenosine stimulated cAMP accumulation in both hA 2B HEK293 and native cells, whereas phospholipase C activation was observed in recombinant receptors and endogenous subtypes expressed in neutrophils but not in lymphocytes. MRE 2029-F20 was revealed to be a potent antagonist in counteracting the agonist effect in both signal transduction pathways. In conclusion, [ 3 H]MRE 2029-F20 is a selective and high-affinity radioligand for the hA 2B adenosine subtype and may be used to quantify A 2B endogenous receptors. In this work, we demonstrated their presence and functional coupling in neutrophils and lymphocytes that play a role in inflammatory processes in which A 2B receptors may be involved.Adenosine is a ubiquitous modulator that exerts its physiological functions through the interaction with four G protein-coupled receptors classified as A 1 , A 2A , A 2B , and A 3 Article, publication date, and citation information can be found at

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